The V8 Owners Forum -

Before i decide what radiator to purchase for my defender i need to know if its really necessary to cool the engine oil?
I already intend to cool the gearbox by using a cooler but this is a separate cooler that fits in front of the main radiator.

Probably depends on what engine you have (tuned or not) how you drive it and what you do with it! I have a 4.2 in my 90 and have a 50th aniversary radiator (big thick one) with an oil cooler and the oil seems to sit between 80 and 90 no matter what I am doing which is Ok. I remember my old 3.5 and would regularly see over 100 deg without oil cooler.

Old TD radiators are cheap (even new) work and have an oil cooler built in.

Toby

Hi
If you stick a sump gaurd on it then yes I would add an oil cooler, an oil temperature below 100C seems a bit cold to me, that is if the gauge is accurate of cause, I would be happier seeing oil (genuine) temperatures around 110-120 otherwise you get condensation in the oil that never boils off, also you are throwing away power with cold oil.
Best regards
Mike

I run a 19J TD radiator in mine with the oil cooler built in (110 3.9 AUTO)

Both the range rover and discovery have oil coolers so I would say the defender would also need one as its a similar weight.

I had the same question when I built my car, do I need an oil cooler? I thought the same as above in that the engine has one in the range rover, but that weights 3 times more than my car. In the end I went without thinking I would check my temps and if it gets too hot then I can add one later. Well the oil temps are perfect upto just over 100. Whenever my car does work it goes fast so I get a lot of air cooling, but in a landrover you can be doing a lot of work mud plugging and towing going slow so very little air cooling.

Tom.

The last time I spoke to the Castrol lubrication Scheduler (this was also confirmed by a Shell also) at my old work, he suggested that magnatec while still with in limits should not run above 120 deg C and what they tend to work on is the oil should run 10 deg C above coolant temperature ( I think I have read this in some V8 publication also, but cannot comment on its correctness) I have a 82 deg thermostate, so I am slighty cool which so far in my engines life has not been detrimental. The large and small marine diesels that I have worked on would run the oil cooler than the coolant temperature and when heated to go through the purifiers would only be heated to 90 deg C maximium.

If you only do short trips then keeping the oil warm may be beneficial, but anything else, I would say fit an oil cooler, as already said a TD rad seems perfect for a V8 and may also heat the oil aswell as cool it.

Toby

Remember the temp you see on the gauge is only a spot temp, likely to be cool from sump, hottest spilling out of bearings, coolest at return from cooler...

I run an oil cooler with my 4.6 in my Rover car, and typically see a 10 degree C increase over the coolant temperature. In my case the oil temp is measured at the base of the sump.

My original 3.5 litre engine had no oil cooler, the highest oil temp I noted was on a 36 degree C day in Sydney traffic, 125 degree C and the coolant temp was close to if not over 100 degrees C.

The oil temp in the bearings as was mentioned above can be noticably higher than in the sump, a good 40 degrees C or more being typical.

Ron.

Very true about the position of the oil temp sender, my one is in the sump, but in the back and the sender is insulated to try and negate the cooling effect from the wind. Reads not far out compared with laser thermometer.

Toby

Surely the simple way is to have a cooler fitted and have a thermostat take off to the cooler.

If the oil gets hot (to the level the cooler thermostat opens) then the oil flow is via the cooler. If not it is just a redundant safety device.

That said I don't run a cooler but perhaps I should - I know the temp sensor is well inn the airflow and in normal use reads 50 degrees - if I saw this at up to say 70 I would be looking for somewhere to pull over and have a look see!

Ian